The present invention relates to a method for manufacturing a one-way clutch cage to be used in, for example, transmissions of automobiles or the like.
Conventionally, there has been a method for manufacturing a one-way clutch cage as shown in FIGS. 4AnF and 5A to 5C. In this manufacturing method, first, as shown in FIG. 4A, a disc 101 is punched out from a metal plate. Next, as shown in FIG. 4B, central part of the disc 101 is drawn by drawing process and a bottom thereof is punched out, by which a circular-cylindrical member 102 is formed. This cylindrical member 102 is composed of a cylindrical portion 103 and an outer flange 105 located at an axial end of the cylindrical portion 103.
Next, as shown in FIG. 4C, a plurality of windows 107, 107, . . . are punched out in the cylindrical portion 103 of the cylindrical member 102 so as to be circumferentially spaced from one another with specified intervals. Subsequently, as shown in FIG. 4D, an outer annular part 106 ranging from the radially outermost circumference of outer flange 105 to a radially inward location, defined by a specified length from the radially innermost circumference of the outer flange 105, towards the radially outermost circumference of the outer flange 105 is punched out of the outer flange 105 of the cylindrical member 102.
Next, as shown in FIGS. 4E and 5C, four circumferential places of the cylindrical member 102 are punched from an inside of the cylindrical member to the outside thereof, so that slits 108 are formed which range across the outer flange 105 to the windows 107. One window 107 is sandwiched by one pair of adjacent slits 108, 108, while another window 107 opposite to the one window 107 is sandwiched by the other pair of adjacent slits 108, 108.
Next, as shown in FIG. 4F, pillars 110, 110 beside the windows 107 sandwiched by the aforementioned pairs of slits 108, 108 are tilted radially outward so that a rim portion 111 sandwiched by the pairs of slits 108, 108 respectively, protrudes radially outward. These rim portions 111, when the one-way clutch is assembled to an outer ring (not shown), press the inner circumferential surface of the outer ring so that a cage 112 is frictionally coupled to the outer ring.
The above-described method for manufacturing a one-way clutch cage, unfortunately, has the following problems (1), (2) and (3):
(1) In the slit punch-out process of FIG. 4E, because a punch 200 is thrust out from the radial inside to the radial outside of the cylindrical member 102 to form the slits 108 as shown in FIGS. 5B and 5C, the total punching distance includes a disc thickness t plus a radial distance D of the outer flange 105 resulting after the cutout of the outer annular part 106. Such a long punching distance causes a need for increasing the punching width in terms of the punching die life, which in turn makes the slit width wider so that another cage is more likely to be caught in this slit 108, resulting in a disadvantage of difficulty in handling. Also, a wide slit width results in a lower strength, whereby the cage 112 becomes prone to deformation. This is a further disadvantage; PA1 (2) As shown in FIG. 5A, during the slit punch-out process, there is a tendency toward the occurrence of burrs in the windows 107. This illustrates another disadvantage; and PA1 (3) In the slit punch-out process, because of a large slit width as described in (1) above, the windows 107 are prone to deformation so that when the cage is assembled to a one-way clutch, the sprag deteriorates in operation and the one-way clutch deteriorates in performance as a disadvantage. PA1 a slit forming step for forming slits in a cylindrical member having a cylindrical portion and an outer flange at an axial end of the cylindrical portion, so that the slits extend radially inward from a location which is radially inward from an outer edge of the outer flange by a specified distance, and also extend axially from the axial end of the cylindrical portion a specified distance; and PA1 an outer flange cutting step for, after the slit forming step, cutting an outer annular part out of the outer flange so that the outer annular part extends from a location which is radially inner the radially outermost end of the slits by a specified distance, to a radially outermost circumference of the outer flange.